i just finished my rear disc install "tbird rear disck conversion" and now I cant lock up the brakes. it feels really close to wanting too lock up but just wont, it stops okay but feels like it needs just a little bit more, I have my adj proportioning valve adjusted all the way in, leaving me no more adjustment, I have a 93 cobra master cylinder 1" bore, with stock front brakes, any ideas on what I can do? adjust the pushrod? anything?
cant lock up brakes after rear disc install
- Thread starter Raginstang
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On that 93 Cobra master cylinder, is it capped off on the end, or does it have a little rubber piece in it. I had this same problem on my upgrade although I didn't use a Cobra master cylinder. Mine was out of a 98' and I had to buy that solid cap -vs- what the 91 came with.
Sorry, I also had to gut my master cylinder as well on the 91'
Sean
Sorry, I also had to gut my master cylinder as well on the 91'
Sean
Raginstang,
Sorry. I meant the proportioning valve (mounted on strut tower where all the brake lines run into). This is what needs to be gutted and a solid plug put into the end of it, not the master cylinder. Ford calls this a proportioning valve as well. Hope this helps.
Mine: 91 GT with 5-lug conversion (from a 98') Summit adjustable propotioning valve, Cobra fronts, 91 gutted and capped Ford proportioning valve, and stock 91 master cylinder.
Sorry. I meant the proportioning valve (mounted on strut tower where all the brake lines run into). This is what needs to be gutted and a solid plug put into the end of it, not the master cylinder. Ford calls this a proportioning valve as well. Hope this helps.
Mine: 91 GT with 5-lug conversion (from a 98') Summit adjustable propotioning valve, Cobra fronts, 91 gutted and capped Ford proportioning valve, and stock 91 master cylinder.
I have already gutted the valve and installed the ford cap on the end, I have a 93 cobra master cylinder, willwood adj proportioning valve in the brake line above the pass firewall were the connector is, t bird rear end with brakes and stock front calipers. any other reasons why it might not lock up? I have the valve at fully open
DId you use the FMS M2450A plug and gut the stock PV from the combination valve?
Also did you purchase this rear end used? How about the calipers? you sure that they are not damaged -- ie the self adjusting clutches in them? How did you compress the piston?
Also how/what did you do to convert from a 3 port to a 2 port master cylinder?
does pumping the pedal help?
Also did you purchase this rear end used? How about the calipers? you sure that they are not damaged -- ie the self adjusting clutches in them? How did you compress the piston?
Also how/what did you do to convert from a 3 port to a 2 port master cylinder?
does pumping the pedal help?
bmorrisj
Member
Been there and done that! With success!
Your brake pedal may be very hard and almost impossible to lock up the brakes. I had to replace the front calipers with 73 mm calipers from a 91 Lincoln Mark 7 to get the braking performance up to par When I did the Turbo Coupe disk brake rear end swap. The car just didn't feel like it wanted to stop, & I did the M/C & proportition valve work according to Matt90GT's site, http://www.svo73mm.cjb.net/.
After the front caliper change, it was night and day better, The brakes work great now, with just the right amount of feel and boost. They should have been standard equipment from the factory.
Some people will tell you to change the booster, but you don't need to do it. The 73 mm calipers are cheap (about $20 each exchange) and work great.
Your brake pedal may be very hard and almost impossible to lock up the brakes. I had to replace the front calipers with 73 mm calipers from a 91 Lincoln Mark 7 to get the braking performance up to par When I did the Turbo Coupe disk brake rear end swap. The car just didn't feel like it wanted to stop, & I did the M/C & proportition valve work according to Matt90GT's site, http://www.svo73mm.cjb.net/.
After the front caliper change, it was night and day better, The brakes work great now, with just the right amount of feel and boost. They should have been standard equipment from the factory.
Some people will tell you to change the booster, but you don't need to do it. The 73 mm calipers are cheap (about $20 each exchange) and work great.
Matt90: yes the rear end is used, and I got NEW calipers for the rear so that I knew for sure they were good. also, all the parts I ordered from you, I got the master cylinder conversion kit, adapter fittings for the rear, and the fms plug kit from summit.
Jrichker, I will try the 73 mm pistons, if it worked for you might work for me, and I wanted to use those anywayz. thanks.. anymore info still appreciated. and no, I didn't change my booster it is stock.
Jrichker, I will try the 73 mm pistons, if it worked for you might work for me, and I wanted to use those anywayz. thanks.. anymore info still appreciated. and no, I didn't change my booster it is stock.
Well reman calipers may still be the problem. Read up on the MP brakes website about the self adjusting clutches in the rear calipers with Ebrakes.
FYI talking locking up brakes is a jackass thing to say. Locking the brakes or spiking them tells you nothing about how the system is working. IF you want to say how the system is working, then measure the hydraulic pressure at each caliper and the vaccum at the booster. Read up on the baer FAQs for more help there.
FYI talking locking up brakes is a jackass thing to say. Locking the brakes or spiking them tells you nothing about how the system is working. IF you want to say how the system is working, then measure the hydraulic pressure at each caliper and the vaccum at the booster. Read up on the baer FAQs for more help there.
I believe that what Raginstang is referring to is the feeling that he has run out of pedal pressure. He & I had the same problem, it just took all your effort to stop the car. Before I did the 73 MM caliper upgrade, I was afraid that there would come a time that I would have to stop quickly and would not be able to press the brake pedal hard enough to make it happen.
The 73 MM caliper upgrade fixed the problem for me, and I think it will work well for him too.
Joe R.
The 73 MM caliper upgrade fixed the problem for me, and I think it will work well for him too.
Joe R.
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